The present invention is directed to operation of power supply apparatuses, and especially to start up operations of power supply apparatuses involving a plurality of supply voltage signals.
By way of example, and not by way of limitation, there are DC-DC converter products that use a variety of different supply voltages in different portions of the circuitry. In such products it is sometimes important to carefully control start up of the device, and hence start up of the power supplied for the device. It is important to ensure that the various voltages are provided in a controlled manner.
The apparatus and method of the present invention ensure that a variety of power supply portions of a power supply apparatus start up and deliver their respective voltages in a predetermined fashion. Specifically, the present invention ensures that the voltages rise together. The voltages follow a common reference signal to ensure that they track together toward their respective steady state supply levels.
Thus, the present invention is a control circuit for a multi-output power supply, or for outputs from multiple power supplies, for use during start up of the power supply.
Prior art power supplies provide an output voltage compensator circuit to track the output voltage and maintain it at a steady level as the load may change. A comparator is commonly employed in an output voltage compensator circuit for receiving a reference voltage at a first input terminal and receiving an output voltage of the power supply being controlled at a second input terminal. An error signal indicating the differences between the signals received at the two input terminals is typically used to drive a pulse width modulation circuit for controlling output of the power supply at a substantially constant steady state value. It is during the start up of the power supply while voltages are rising toward their respective steady state values that some products are at risk.
Prior art attempts to regulate start up of a power supply have typically focused on controlling ramp-up of the reference voltage provided at the first input terminal of the comparator in the output voltage compensator circuit. Prior art power supplies provide supply voltages to various portions of a product or to various devices in a product without coordination in a manner by which the various supply voltages proceed independently to reach their respective different steady state voltage supply levels at substantially the same time. As a result there is often an unacceptably large difference between voltage supply levels at a given time during start up.
There is a need for an apparatus and method for effecting a coordinated ramping up of supply voltages substantially together for various portions of a product or various devices in a product to operating levels.
An apparatus for effecting controlled start up of a plurality of supply voltage signals received from at least one power supply device responds to feedback control by at least one feedback signal in producing the plurality of supply voltage signals and includes: (a) a plurality of first error amplifier devices; each respective error amplifier device of the plurality of first error amplifier devices receives a respective supply voltage signal of the plurality of supply voltage signals at a first input terminal; each respective first error amplifier device receives a first reference voltage signal at a second input terminal; each respective first error amplifier device generates a respective first error output signal on a respective first output line; the respective first error output signal indicates a first difference between the respective supply voltage signal and the first reference voltage signal; each respective first error output line is coupled with a respective switching device; and (b) a plurality of second error amplifier devices; each respective error amplifier device of the plurality of second error amplifier devices has a first input node and a second input node; the first input node is coupled with the respective switching device and is coupled for receiving the respective supply voltage signal; the first input node receives a sum of the respective first error output signal and the respective supply voltage signal when the respective switching device is in a first operational orientation; the first input node receives the respective supply voltage signal when the respective switching device is in a second operational orientation; the respective second error amplifier device receives a second reference voltage at a second input node; the respective second error amplifier device provides a second error output signal indicating a second difference between signals received at the first input node and the second input node; the second error output signal is a respective feedback signal of the at least one feedback signal for effecting the feedback control of the at least one power supply device.
A method for effecting controlled start up of a plurality of supply voltage signals, the plurality of supply voltage signals being received from at least one power supply device responding to feedback control by at least one feedback signal in producing the plurality of supply voltage signals, includes the steps of: (a) providing a plurality of first error amplifier devices; each respective first error amplifier device of the plurality of first error amplifier devices receiving a respective supply voltage signal of the plurality of supply voltage signals at a first input terminal; each of the respective first error amplifier devices receiving a first reference voltage signal at a second input terminal; each of the respective first error amplifier devices generating a respective first error output signal on a respective first output line; the respective first error output signal indicating a first difference between the respective supply voltage signal and the first reference voltage signal; each of the respective first error output lines being coupled with a respective switching device; (b) providing a plurality of second error amplifier devices; each respective second error amplifier device of the plurality of second error amplifier devices having a first input node and a second input node; the first input node being coupled with the respective switching device and being coupled for receiving the respective supply voltage signal; the first input node receiving a sum of the respective first error output signal and the respective supply voltage signal when the respective switching device is in a first operational orientation; the first input node receiving the respective supply voltage signal when the respective switching device is in a second operational orientation; the respective second error amplifier device receiving a second reference voltage at a second input node; the respective second error amplifier device providing a second error output signal indicating a second difference between signals received at the first input node and the second input node; the second error output signal being a respective feedback signal of the at least one feedback signal for effecting the feedback control of the at least one power supply device; (c) establishing the respective switching device in the first operational orientation until the respective supply voltage signal rises to a predetermined value; and (d) establishing the respective switching device in the second operational orientation.
It is, therefore, an object of the present invention to provide an apparatus and method for effecting a coordinated ramping-up of supply voltages substantially together for various portions of a product or various devices in a product to operating levels.
Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention.